Ink jet printing systems are known in which a printhead includes a jetting module that defines one or more rows of nozzles in a nozzle plate which receive a recording fluid, such as a water-based ink, from a pressurized fluid supply manifold and eject the ink in rows of parallel streams. Such printing systems achieve image production by allowing drops which are to be printed to contact the recording medium and deflecting drops that are not to be printed to a drop catcher device.
Conventional methods for assembling the components of a printhead include locating the jetting module or drop generator with the aid of an assembly fixture, then using an adhesive such as epoxy to fasten it in place. A charge plate/catcher assembly is then aligned to the drop generator using external adjustment fixtures. Once a proper alignment is achieved, the charge plate/catcher assembly is fastened with screws or adhesive to the common frame holding the drop generator.
Traditional systems allow replacement of a printhead by creating field replaceable units which includes a jetting module, a charge plate, and a catcher. Some field replaceable units also include fluid system components such as valves and pressure and temperature sensors, and support electronics for the inkjet module. As the number of jets to be controlled increased, it became impractical to connect each charge electrode in the field replaceable printhead to the controlling charge driver electronics that were not part of the field replaceable printhead. In such printheads, it became preferable to include charge driver electronics in the field replaceable unit. As the charge plate was also subject to failure, such field replaceable units were preferable because, in addition to the jetting module, the charge plate was also field replaceable.
Unfortunately, existing assembly and alignment methods have several drawbacks. For example, using an adhesive increases assembly time because it takes several hours for the adhesive to cure and using epoxy is problematic because epoxy is sensitive to heat and humidity. Additionally, the final fastening of the charge plate/catcher assembly alters the alignment, usually requiring realignment.
High costs of shipping make it advantageous to replace only the jetting module rather then the entire printhead. Additionally, jetting modules providing higher resolution require high precision alignment. Accordingly, there is a need for a jetting module to be a field replaceable unit that an be properly aligned during installation.